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Oracle Argus Safety Installation Guide Release 7.0.3 E40575-02 |
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# 9 Enabling IIS HTTP Compression

This chapter describes how to enable IIS HTTP Compression on a Windows 2008 Server.

This feature is required when the pipeline between the Web Server and the IIS Client have low bandwidth or have high amounts of data usage.

This chapter includes discussions of the following:

- IIS Web Page Compression

- IIS Caching Settings

- Local Internet Explorer (IE) Client Caching Settings

## IIS Web Page Compression

This section includes the following sections:

- HTTP Compression

- Known Effects of Enabling Compression

- How to Enable HTTP Compression

### HTTP Compression

By default, HTTP compression is disabled in Windows 2008 but can be enabled as necessary. Reasons for enabling compression include the following:

- The bandwidth between the IIS Web Server and the IE Client(s) is of a low speed.

- The bandwidth between the IIS Web Server and the IE Client(s) is high speed but has high utilization.

- Reducing overall traffic between the IIS Web Server and the IE Client(s).

### Known Effects of Enabling Compression

Although implementing IIS Compression proves to be of value to the customer, there is a increase in CPU usage on the Web Server. When compression is enabled, every time a non static page (ASP, ASPX) is requested, the page is compressed on the fly before sending to the client. This puts some overhead on the Web Server CPU however, based on internal testing web server load is usually very minimum. Static Pages such as HTML, JS, HTM pages are compressed only once and then stored in a cache on the Web Server for later requests.

Due to the above, the Web Servers should be monitored to prevent a CPU bottleneck from occurring which would decrease performance rather than increasing it.

### How to Enable HTTP Compression

Use the following procedure to enabled HTTP Compression in IIS 7:

1. Open ”Internet Information Services (IIS) manager” from Control Panel -> Administrator Tools.

2. Browse to the ”Argus Safety Web” web site.

3. Double click ”Compression” in the Features View.

4. Check both options:

   - Enable dynamic content compression

   - Enable static content compression

     Note: To enable compression, the feature option must be installed as part of the Windows installation.

## IIS Caching Settings

This section includes discussions on the following:

- IIS Caching

- Known Effects of Enabling Caching

- How to Enable Caching

### IIS Caching

IIS Caching is supported in Windows 2008. IIS Caching is required to prevent the web server from having to re-serve certain files to the IE Client when the file has not changed. In other words, files such as Images do not change on a day-to-day basis and once they are sent to the IE client they should not be sent again each time the client requests the file. The local IE client should keep a local cache copy of the file and use the local file instead.

Before IIS Caching will function properly:

- IIS must be set up properly

- The local IE client settings must be set up correctly

### Known Effects of Enabling Caching

Currently, there are currently no known effects of enabling caching on the Web Server. However, enabling cache should only be used on files / folders where the files are not dynamic or do not change daily. Certain files, such as .ASP and .ASPX files, should never be cached.

### How to Enable Caching

Use the following procedure to enable / verify IIS caching (Default is turned on from Argus Installation):

1. Open ”Internet Information Services (IIS) manager” from Control Panel -> Administrator Tools.

2. Browse to the ”Argus Safety Web” website.

3. Double click the ”HTTP Response Headers” option.

4. Ensure ”Cache Control” header with value of ”no-cache” exists.

5. Click the ”Set Common Headers” option.

6. Ensure that ”Expire Web Content” is checked and the option ”Immediately” is selected.

7. Apply and changes.

8. Click on the ”PDFReports” Folder.

9. Double click the ”HTTP Response Headers” option.

10. Ensure ”Cache Control” header does not exist.

11. Click the ”Set Common Headers” option.

12. Ensure that ”Expire Web Content” is unchecked.

13. Repeat the same steps for ”UploadedLetters” (Steps 9-12)

14. For each of the following folders, the same settings exist (Steps 9-12). In addition, verify on the ”Set Common Headers”, the ”After” option is selected and configured for the specified number of days as seen next to each folder below:

    - Css – 15 Days Expiration

    - Js – 1 Day Expiration

    - Img – 15 Days Expiration

## Local Internet Explorer (IE) Client Caching Settings

This section includes information about the following:

- IE Client Caching

- IE Client Caching Tab Options

- How to Enable IE Caching

### IE Client Caching

IE Caching works directly with IIS Caching. If IIS Caching is used, you must turn on IE Client Caching otherwise caching will not occur.

### IE Client Caching Tab Options

In IE Client, there are some options on the caching tab that you should be aware of. The following table lists and describes IE Caching Tab Options.

Option | Description
--- | ---
Every Time I visit the Web Page | Selecting this option will not cache a single file. Every time a file is requested, IE will request the Server to re-send all files. This option should never be used as performance will suffer severely
Every Time I Start Internet Explorer | Selecting this option will cache files only until the browser is closed. Upon closing the IE window, all cache will be expired. This option will provide some performance enhancement when a user visits the same page multiple times within a single browser session
Automatically | Selecting this option will allow IE to make a decision if a file should be cached or not. This option automatically performs the same function as "Every Time I Start Internet Explorer". In addition, after a file has been request so many time, IE will automatically cache the file even after the browser is closed. If the file has been cached and a new version of the file exists on the Web Server, the new version will be downloaded to the client. This is the option that should be used for best performance.
Never | Selecting this option will cause IE to always cache every file which can cause problem with sites that have dynamic data and so this should not be used. Also, if a file has been updated on the server due to an upgrade, the new file will not be sent to the client.

### How to Enable IE Caching

Use the following procedure to enable IE caching:

1. Open Internet Explorer.

2. Select Tools=> Internet Options.

3. When the Internet Options dialog box opens:

   - Select the "General" Tab.

   - Locate the Browsing history section and click Settings.

4. When the Temporary Internet Files and History Settings dialog box opens:

   - Select Automatically.

   - Click OK.

5. Close the Internet Explorer browser and restart it to begin caching.